A system and method for transaction bitcoin is described. Bitcoin can be sent to an email address. No miner's fee is paid by a host computer system. Hot wallet functionality is provided that transfers values of some Bitcoin addresses to a vault for purposes of security. A private key of a Bitcoin address of the vault is split and distributed to keep the vault secure. Instant exchange allows for merchants and customers to lock in a local currency price. A vault has multiple email addresses to authorize a transfer of bitcoin out of the vault. User can opt to have private keys stored in locations that are under their control. A tip button rewards content creators for their efforts. A bitcoin exchange allows for users to set prices that they are willing to sell or buy bitcoin and execute such trades.